Abstract: A rotary type internal combustion engine having stationary stator housing and a rotor, which is rotatably mounted within the stator housing. The rotor has a thrust face, which is exposed to combusted gases within the engine. The thrust face has a variable surface area. The stator has a profiled inner surface or a contoured end cap which varies the surface area of the thrust face exposed to combusting gases and thus provides the engine with a required torque characteristic.

Abstract: A rotary engine, motor, compressor or pump having a stator housing (101) and a rotor (102). A variable volume working chamber is formed between the stator housing (101), rotor (102), thrust face (176) of moveable arm (116) and the thrust face of moveable arm (118). The surface area of thrust face (176) varies with the varying profile of the stator housing inner surface (166) as the rotor (102) rotates to provide a desired torque characteristic. The surface area of the thrust face of moveable arm (118) is constant during at least part of the working cycle.